1. Technical Field
An aspect of the present invention relates to integrated circuit devices and electronic equipment.
2. Related Art
High definition imaging technology, such as, high-vision imaging technology has become popular in recent years, and with such a technological trend, higher definition and greater multi-grayscale displays have been achieved in display equipment (electronic equipment) such as liquid crystal projectors and the like. Such display equipment with greater multi-grayscale requires analog circuits with high accuracy in their drivers to drive liquid crystal panels (electro-optical panels).
More specifically, the greater the number of grayscale levels, the smaller the grayscale voltage for each grayscale level, such that the grayscales would not be correctly presented if a slight error occurs in the driving voltage of the driver. For example, when an offset difference is present in the operation amplifiers that drive adjacent ones of data voltage supply lines (data lines, source lines), a difference occurs in the voltages on the adjacent data voltage supply lines, which may be viewed as a vertical line on the displayed image. In this respect, drivers that are used for display equipment with multiple grayscales need to address an issue of accurately outputting data voltages.
In order to address the issue described above, for example, Japanese patent 3405333 (Patent Document 1) describes a method for improving the accuracy in data voltages through driving data voltage supply lines by operation amplifiers and then by DAC outputs. According to this method, by driving the data voltage supply lines with DAC outputs, occurrence of differences in data voltages due to offsets of the operation amplifiers can be prevented.
However, the higher the definition of a liquid crystal panel, the faster the drive data voltage supply lines need to be driven. The method described in Patent Document 1 uses DAC outputs with higher output impedance, compared to those of the operation amplifiers, and therefore entails a problem in that it takes a relatively long time for each data voltage to reach a desired grayscale voltage.
On the other hand, Japanese Laid-open Patent Application 2002-108298 (Patent Document 2) describes a method for correcting unevenness in the display of a liquid crystal projector, through generating correction data stored in a RAM in an interpolation operation and adding the generated correction data to picture data. According to this method, by correcting display data by digital processing, data voltages can be accurately outputted, and high-speed driving by operation amplifiers with high driving power is possible.
However, the characteristics of liquid crystal panels and drivers deteriorate with passing of time after having been shipped out. Also, the characteristics would change due to heat generated by the display equipment such as projector lamps or the like. The method described in Patent Document 2 uses correction data adjusted at the time of manufacturing liquid crystal panels for the correction, and therefore entails a problem in that changes in the characteristics that occur after shipping cannot be accommodated.